New SB2 orbital elements for accurate masses with Gaia: HD 9312, HD 9313 and HD 183255

info:eu-repo/semantics/published

A peculiar metal-rich star, HD 135485

Local thermodynamic equilibrium (LTE) absolute and differential abundances are presented for a peculiar metal-rich B-type star, HD 135485. These suggest that HD 135485 has a general enrichment of similar to0.5 dex in all the metals observed (C, N, O, Ne, Mg, Al, Si, P, S, Cl, Ar, Sc, Ti, Cr, Mn, Fe and Sr), except for nickel. The helium enhancement and hence hydrogen deficiency can account for less than or equal to 0.2 dex of this enhancement of metals, with the additional enhancement probably being representative of the progenitor gas. However, some of the metals appear to have greater enhancements, which may have occurred during the star's evolution. The significantly larger nitrogen abundance coupled with a modest helium enhancement observed in HD 135485 indicates that carbon- nitrogen (CN) processed material has possibly contaminated the stellar surface. Neon and carbon enhancements may indicate that helium core flashes have also occurred in HD 135485. Some of the iron-group elements (viz. Mn and Ni) appear to have similar abundance patterns to that of silicon Ap stars, but it is uncertain how these abundance patterns formed if they were not present in the progenitor gas. From a kinematical investigation it is unclear whether this star formed in a metal-rich region as implied by its chemical composition. From its position in the Hertzsprung-Russell diagram, HD 135485 would appear to be an evolved star lying close to or on the horizontal branch.

Above Threshold Dissociation of Vibrationally Cold HD+ Molecules

The experimental study of molecular dissociation of H2+ by intense laser pulses is complicated by the fact that the ions are initially produced in a wide range of vibrational states, each of which responds differently to the laser field. An electrostatic storage device has been used to radiatively cool HD+ ions enabling the observation of above threshold dissociation from the ground vibrational state by 40 fs laser pulses at 800 nm. At the highest intensities used, dissociation through the absorption of at least four photons is found to be the dominant process.

The masses and radii of HD 186753B and TYC7096-222-1B: the discovery of two M-dwarfs that eclipse A-type stars

We present observations of two new single-lined eclipsing binaries, both consisting of an Am star and an M-dwarf, discovered by the Wide Angle Search for Planets transit photometry survey. Using WASP photometry and spectroscopic measurements we find that HD 186753B has an orbital period of P=1.9194 days, a mass of M=0.24±0.02~M? and radius of R=0.31+0.06-0.06~R?; and that TCY7096-222-1B has an orbital period of P=8.9582 days, a mass of between 0.29 and 0.54 M? depending on eccentricity and radius of R=0.263+0.02-0.07~R?. We find that the Am stars have relatively low rotational velocities that closely match the orbital velocities of the M-dwarfs, suggesting that they have been “spun-down” by the M-dwarfs.

Tight constraints on the existence of additional planets around HD 189733†

We report a transit timing study of the transiting exoplanetary system HD 189733. In total, we observed 10 transits in 2006 and 2008 with the 2.6-m Nordic Optical Telescope, and two transits in 2007 with the 4.2-m William Herschel Telescope. We used Markov Chain Monte Carlo simulations to derive the system parameters and their uncertainties, and our results are in a good agreement with previously published values. We performed two independent analyses of transit timing residuals to place upper mass limits on putative perturbing planets. The results show no evidence for the presence of planets down to 1 Earth mass near the 1:2 and 2:1 resonance orbits, and planets down to 2.2 Earth masses near the 3:5 and 5:3 resonance orbits with HD 189733b. These are the strongest limits to date on the presence of other planets in this system. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. ‡

Evidence for a modifier of onset age in Huntington disease linked to the HD gene in 4p16

Huntington disease (HD) is a neurodegenerative disorder caused by the abnormal expansion of CAG repeats in the HD gene on chromosome 4p16.3. A recent genome scan for genetic modifiers of age at onset of motor symptoms (AO) in HD suggests that one modifier may reside in the region close to the HD gene itself. We used data from 535 HD participants of the New England Huntington cohort and the HD MAPS cohort to assess whether AO was influenced by any of the three markers in the 4p16 region: MSX1 (Drosophila homeo box homologue 1, formerly known as homeo box 7, HOX7), Delta2642 (within the HD coding sequence), and BJ56 (D4S127). Suggestive evidence for an association was seen between MSX1 alleles and AO, after adjustment for normal CAG repeat, expanded repeat, and their product term (model P value 0.079). Of the variance of AO that was not accounted for by HD and normal CAG repeats, 0.8% could be attributed to the MSX1 genotype. Individuals with MSX1 genotype 3/3 tended to have younger AO. No association was found between Delta2642 (P=0.44) and BJ56 (P=0.73) and AO. This study supports previous studies suggesting that there may be a significant genetic modifier for AO in HD in the 4p16 region. Furthermore, the modifier may be present on both HD and normal chromosomes bearing the 3 allele of the MSX1 marker.

ALMA hints at the presence of two companions in the disk around HD 100546

HD 100546 is a well-studied Herbig Be star-disk system that likely hosts a close-in companion with compelling observational evidence for an embedded protoplanet at 68 AU. We present ALMA observations of the HD 100546 disk which resolve, for the first time, the gas and dust structure at (sub)mm wavelengths. The CO emission (at 345.795 GHz) originates from an extensive molecular disk (390 AU in radius) whereas the continuum emission is more compact (230 AU in radius) suggesting radial drift of the mm-sized grains. The CO emission is similar in extent to scattered light images indicating well-mixed gas and um-sized grains in the disk atmosphere. Assuming an azimuthally-symmetric disk, the continuum visibilities at long baselines (> 100 klambda) are reproduced by a compact ring with a width of 21 AU centered at 26 AU. An outer component is required to fit the short baselines: assuming a flat brightness distribution, the best-fit model is a ring with a width of 75 AU centered at 190 AU. The influence of a companion and protoplanet on the dust evolution is investigated. The companion at 10 AU facilitates the accumulation of mm-sized grains within a compact ring, ~20-30 AU, by ~10 Myr. The injection of a protoplanet at 1 Myr hastens the ring formation (~1.2 Myr) and also triggers the development of an outer ring (~100-200 AU). These observations provide additional evidence for the presence of a close-in companion and hint at dynamical clearing by a protoplanet at 68 AU.

The structure of an unconventional HD-GYP protein from Bdellovibrio reveals the roles of conserved residues in this class of cyclic-di-GMP phosphodiesterases

UNLABELLED: Cyclic-di-GMP is a near-ubiquitous bacterial second messenger that is important in localized signal transmission during the control of various processes, including virulence and switching between planktonic and biofilm-based lifestyles. Cyclic-di-GMP is synthesized by GGDEF diguanylate cyclases and hydrolyzed by EAL or HD-GYP phosphodiesterases, with each functional domain often appended to distinct sensory modules. HD-GYP domain proteins have resisted structural analysis, but here we present the first structural representative of this family (1.28 Å), obtained using the unusual Bd1817 HD-GYP protein from the predatory bacterium Bdellovibrio bacteriovorus. Bd1817 lacks the active-site tyrosine present in most HD-GYP family members yet remains an excellent model of their features, sharing 48% sequence similarity with the archetype RpfG. The protein structure is highly modular and thus provides a basis for delineating domain boundaries in other stimulus-dependent homologues. Conserved residues in the HD-GYP family cluster around a binuclear metal center, which is observed complexed to a molecule of phosphate, providing information on the mode of hydroxide ion attack on substrate. The fold and active site of the HD-GYP domain are different from those of EAL proteins, and restricted access to the active-site cleft is indicative of a different mode of activity regulation. The region encompassing the GYP motif has a novel conformation and is surface exposed and available for complexation with binding partners, including GGDEF proteins.

IMPORTANCE: It is becoming apparent that many bacteria use the signaling molecule cyclic-di-GMP to regulate a variety of processes, most notably, transitions between motility and sessility. Importantly, this regulation is central to several traits implicated in chronic disease (adhesion, biofilm formation, and virulence gene expression). The mechanisms of cyclic-di-GMP synthesis via GGDEF enzymes and hydrolysis via EAL enzymes have been suggested by the analysis of several crystal structures, but no information has been available to date for the unrelated HD-GYP class of hydrolases. Here we present the multidomain structure of an unusual member of the HD-GYP family from the predatory bacterium Bdellovibrio bacteriovorus and detail the features that distinguish it from the wider structural family of general HD fold hydrolases. The structure reveals how a binuclear iron center is formed from several conserved residues and provides a basis for understanding HD-GYP family sequence requirements for c-di-GMP hydrolysis.

HD Laser scanning for the evaluation of salt decay laboratory simulations of building limestone

Laboratory salt decay simulations are a well established method to assess the relative durability of stone. There is still, however, very much scope to implement improved monitoring techniques to investigate the changes experienced by the materials during these experiments. Non-destructive techniques have acquired over recent decades a preferential status for monitoring change samples during salt decay tests, as they allow cumulative tests on each sample. The development of HD laser scanning permits detailed mapping of surface changes and, therefore, constitutes an effective technique to monitor non-destructively surface changes in tested samples as an alternative to other monitoring techniques such as traditional weight loss strategies that do not permit any degree of spatial differentiation that can be related, for example, to underlying stone properties.

Transit Observations of the Hot Jupiter HD 189733b at X-Ray Wavelengths

We present new X-ray observations obtained with Chandra ACIS-S of the HD 189733 system, consisting of a K-type star orbited by a transiting Hot Jupiter and an M-type stellar companion. We report a detection of the planetary transit in soft X-rays with a significantly deeper transit depth than observed in the optical. The X-ray data favor a transit depth of 6%-8%, versus a broadband optical transit depth of 2.41%. While we are able to exclude several possible stellar origins for this deep transit, additional observations will be necessary to fully exclude the possibility that coronal inhomogeneities influence the result. From the available data, we interpret the deep X-ray transit to be caused by a thin outer planetary atmosphere which is transparent at optical wavelengths, but dense enough to be opaque to X-rays. The X-ray radius appears to be larger than the radius observed at far-UV wavelengths, most likely due to high temperatures in the outer atmosphere at which hydrogen is mostly ionized. We furthermore detect the stellar companion HD 189733B in X-rays for the first time with an X-ray luminosity of log LX = 26.67 erg s-1. We show that the magnetic activity level of the companion is at odds with the activity level observed for the planet-hosting primary. The discrepancy may be caused by tidal interaction between the Hot Jupiter and its host star.

Recuperación de cepas HD de Bacillus thuringiensis, su propagación en 14 medios de producción y la evaluación de la actividad tóxica contra Trichoplusia ni (Háber) y Heliothis virescens (Fabricius)

Tesis (Maestría en Ciencias con Especialidad en Microbiología) UANL