229 research outputs found
Speckle Imaging of Gamma2 Velorum: The Inner Wind Possibly Resolved
Accurately quantifying the rates dM/dt at which massive stars lose mass is
essential to any understanding of their evolution. All dM/dt estimates to date
assume wind clumping factors; not allowing for clumping leads to overestimates
of dM/dt and underestimates of lifetimes and masses when these stars explode as
supernovae. Mid-IR spectroscopy suggested that the wind of the nearest
Wolf-Rayet star, Gamma2 Vel, is resolved with a Full Width at 10 per cent
intensity of 0.5 arcsec, or 171 AU at the 342 pc distance of the star. As the
Zorro speckle imager on Gemini-South is capable of 0.02 arcsec resolution, we
have used it to image Gamma2 Vel at two orbital phases (0.30 and 0.44) with two
narrowband and two intermediate-band filters in an attempt to resolve its wind.
Our observations demonstrate that the wind of Gamma2 Vel may be resolved as a
0.07 arcsec westward elongation through an 832 nm filter at orbital phase 0.3 .
If confirmed, this is the smallest scale (24 AU) at which a WR star wind
asymmetry has been directly imaged. Similar imaging at multiple phases is
needed to determine if the asymmetry is due to stochastic wind clumping,
co-rotating interaction regions or colliding-wind, cone-shaped shocks.Comment: 7 pages, 4 Figures, in press in MNRA
Introducing the Condor Array Telescope: IV. A possible nova super-remnant surrounding the putative recurrent nova KT Eridani
Just 10 recurrent novae (RNe) - which erupt repeatedly on timescales shorter
than one century - are known in our Galaxy. The most extreme RN known (located
in the Andromeda galaxy), M31N 2008-12a, undergoes a nova eruption every year,
and is surrounded by a vast nova "super-remnant", 134 pc in extent. Simulations
predict that all RNe should be surrounded by similar vast shells, but previous
searches have failed to detect them. KT Eri has recently been suggested to be a
RN, and we have used the Condor Array Telescope to image its environs through
multiple narrowband filters. We report the existence of a large ( 50 pc
diameter), H-bright shell centered on KT Eri, exactly as predicted.
This strongly supports the claim that KT Eri is the 11th Galactic recurrent
nova, and only the second nova known to be surrounded by a super-remnant. SALT
spectra of the super-remnant demonstrate that its velocity width is consistent
with that of M31-2008-12a.Comment: 12 pages, 8 figure
Selective Persistence of HPV Cross-Neutralising Antibodies following Reduced-Dose HPV Vaccine Schedules.
The duration of cross-neutralising antibody responses (cross-NAb) following HPV immunisation is unknown. We compared cross-NAb responses in cohort of girls who were either unimmunised or had received immunisation with one, two or three doses of 4vHPV (Gardasil®,Merck Inc.) six years earlier, before and one month after a booster dose of 2vHPV (Cervarix®, GSK). NAb to potentially cross-reactive HPV genotypes 31, 33, 45, 52 and 58 were measured using a HPV pseudovirion-based neutralisation assay. Girls who had previously received at least one dose of 4vHPV had significantly higher NAb titres for HPV31 when compared with unimmunised girls, whereas no difference in NAb titre was observed for four other genotypes (33, 45, 52 and 58). Following a single further immunisation with 2vHPV, NAb titres to each of the five tested HPV genotypes were comparable for girls who previously received one, two or three doses of 4vHPV, and were significantly higher than for previously unimmunised girls. Immunisation with one, two or three doses of 4vHPV induced NAb to HPV31 that persisted for six years, but there was no persistence of NAb to HPV33, 45, 52 or 58. Our results suggest that one or two doses of 4vHPV may provide long-term protection against HPV31
Life-History Evolution on Tropidurinae Lizards: Influence of Lineage, Body Size and Climate
The study of life history variation is central to the evolutionary theory. In many ectothermic lineages, including lizards, life history traits are plastic and relate to several sources of variation including body size, which is both a factor and a life history trait likely to modulate reproductive parameters. Larger species within a lineage, for example tend to be more fecund and have larger clutch size, but clutch size may also be influenced by climate, independently of body size. Thus, the study of climatic effects on lizard fecundity is mandatory on the current scenario of global climatic change. We asked how body and clutch size have responded to climate through time in a group of tropical lizards, the Tropidurinae, and how these two variables relate to each other. We used both traditional and phylogenetic comparative methods. Body and clutch size are variable within Tropidurinae, and both traits are influenced by phylogenetic position. Across the lineage, species which evolved larger size produce more eggs and neither trait is influenced by temperature components. A climatic component of precipitation, however, relates to larger female body size, and therefore seems to exert an indirect relationship on clutch size. This effect of precipitation on body size is likely a correlate of primary production. A decrease in fecundity is expected for Tropidurinae species on continental landmasses, which are predicted to undergo a decrease in summer rainfall
Taking into account sensory knowledge: the case of geo-techologies for children with visual impairments
This paper argues for designing geo-technologies supporting non-visual sensory knowledge. Sensory knowledge refers to the implicit and explicit knowledge guiding our uses of our senses to understand the world. To support our argument, we build on an 18 months field-study on geography classes for primary school children with visual impairments. Our findings show (1) a paradox in the use of non-visual sensory knowledge: described as fundamental to the geography curriculum, it is mostly kept out of school; (2) that accessible geo-technologies in the literature mainly focus on substituting vision with another modality, rather than enabling teachers to build on children's experiences; (3) the importance of the hearing sense in learning about space. We then introduce a probe, a wrist-worn device enabling children to record audio cues during field-trips. By giving importance to children's hearing skills, it modified existing practices and actors' opinions on non-visual sensory knowledge. We conclude by reflecting on design implications, and the role of technologies in valuing diverse ways of understanding the world
The khmer software package: enabling efficient nucleotide sequence analysis [version 1; referees: 2 approved, 1 approved with reservations]
The khmer package is a freely available software library for working efficiently with fixed length DNA words, or k-mers. khmer provides implementations of a probabilistic k-mer counting data structure, a compressible De Bruijn graph representation, De Bruijn graph partitioning, and digital normalization. khmer is implemented in C++ and Python, and is freely available under the BSD license at https://github.com/dib-lab/khmer/
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