Search

We report the discovery of a wide comoving substellar companion to the nearby (D = 67.5 ± 1.1 pc) A3V star ζ Delphini based on imaging and follow-up spectroscopic observations obtained during the course of our Volume-limited A-Star (VAST) multiplicity survey. ζ Del was observed over a five-year baseline with adaptive optics, revealing the presence of a previously unresolved companion with a proper motion consistent with that of the A-type primary. The age of the ζ Del system was estimated as 525 ± 125 Myr based on the position of the primary on the colour–magnitude and temperature–luminosity diagrams. Using intermediate-resolution near-infrared spectroscopy, the spectrum of ζ Del B is shown to be consistent with a mid-L dwarf (L5 ± 2), at a temperature of 1650 ± 200 K. Combining the measured near-infrared magnitude of ζ Del B with the estimated temperature leads to a model-dependent mass estimate of 50 ± 15 MJup, corresponding to a mass ratio of q = 0.019 ± 0.006. At a projected separation of 910 ± 14 au, ζ Del B is among the most widely separated and extreme-mass ratio substellar companions to a main-sequence star resolved to date, providing a rare empirical constraint of the formation of low-mass ratio companions at extremely wide separations. [ABSTRACT FROM AUTHOR]

ABSTRACT As a part of our ongoing Volume-limited A-Star (VAST) adaptive optics survey, we have obtained observations of 26 binary systems with projected separations <100 au, 13 of which have sufficient historical measurements to allow for refinement of their orbital elements. For each system with an estimated orbit, the dynamical system mass obtained was compared with the system mass estimated from mass-magnitude relations. Discrepancies between the dynamical and theoretical system mass can be explained by the presence of a previously unresolved spectroscopic component or by a non-solar metallicity of the system. Using this approach to infer the presence of additional companions, a lower limit to the fraction of binaries, triples and quadruples can be estimated as 39, 46 and 15 per cent for systems with at least one companion within 100 au. The fraction of multiple systems with three or more components shows a relative increase compared to the fraction for solar-type primaries resolved in previous volume-limited surveys. The observations have also revealed a pair of potentially young (<100 Myr) M dwarf companions, which would make an ideal benchmark for the theoretical models during the pre-main-sequence contraction phase for M dwarfs. In addition to those systems with orbit fits, we report 13 systems for which further orbital monitoring observations are required, 11 of which are newly resolved as a part of the VAST survey. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]

Aims: A triplex real-time PCR assay to quantify Mycoplasma hyopneumoniae in specimens from live and dead pigs was developed and validated. The minimal dose of Myc. hyopneumoniae required to induce pneumonia in specific pathogen-free pigs was determined. Methods and Results: This TaqMan test simultaneously detected three genes encoding the proteins P46, P97 and P102. All Myc. hyopneumoniae strains analysed were detected, including strains isolated in three countries (France, England and Switzerland) and from several pig farms ( n = 33), and the test was specific. The estimated detection thresholds were 1·3 genome equivalents (μl−1) for the targets defined in p97 and p102 genes and 13 genome equivalents (μl−1) for the segment defined in the p46 gene. This test was used to quantify Myc. hyopneumoniae in specimens sampled from experimentally infected pigs. In live pigs, c. 107, 108 and 1010 genome equivalents (ml−1) of Myc. hyopneumoniae were detected in the nasal cavities, tonsils and trachea samples, respectively. In dead pigs, 108–1010 genome equivalents (ml−1) of Myc. hyopneumoniae were detected in the lung tissue with pneumonia. The estimated minimal dose of Myc. hyopneumoniae required to induce pneumonia was 105 colour-changing units (CCU) per pig (corresponding to 108 mycoplasmas). Conclusion: The triplex RT-PCR test was validated and can be used for testing samples taken on the pig farms. Significance and Impact of the Study: This test should be a very useful tool in pig herds to control enzootic pneumonia or healthy carrier pigs and to study the dynamics of Myc. hyopneumoniae infections. [ABSTRACT FROM AUTHOR]

Aims: To examine the variability among Pasteurella multocida strains isolated from pigs (nasal, tonsil and lung specimens) and humans in France. Methods and Results: The genetic diversity of 117 French isolates of P. multocida, obtained from pigs ( n = 101) and humans ( n = 16) and three reference strains, was evaluated by pulsed-field gel electrophoresis (PFGE) after macrorestriction with ApaI. Sixty-four patterns were detected. The genetic relationships revealed five clusters (Aa1, Aa2, Aa3, Ab and B). The pig isolates obtained from pneumonic lungs and nasal cavities were clustered in groups Ab and Aa1, respectively ( P < 0·05). Up to four different PFGE patterns were detected in the same farm. Isolates producing dermonecrotic toxins were clustered only in group Aa1, suggesting that the toxigenic isolates were more genetically homogenous than the others. Conversely, cluster Aa3 was significantly associated with human isolates even if the human isolates are spread over most of the clusters. Conclusions: Pasteurella multocida strains were genetically diverse, but pig and human isolates were significantly clustered in distinct phylogenetic groups. Significance and Impact of the Study: The discrimination index was >0·95 in both populations of human and pig isolates. Therefore, ApaI-PFGE seems to be a useful tool for epidemiological tracing of P. multocida infections. [ABSTRACT FROM AUTHOR]