The effect of rotation on the spectrum of Vega

The discovery that Vega is a rapidly rotating pole-on star has raised a number of questions about this fundamental standard, including such issues as its composition, and in turn its mass and age. We report here a reanalysis of Vega's composition. A full spectral synthesis based on the Roche model derived earlier from NPOI interferometry is used. We find the line shapes in Vega's spectrum to be more complex than just flat-bottomed, which have been previously reported; profiles range from slightly self-reversed to simple ``V'' shapes. A high SNR spectrum, obtained by stacking spectra from the ELODIE archive, shows excellent agreement with the calculations, provided we add about 10 km/s of macroturbulence to the predicted spectra. From the abundance analysis, we find that Vega shows the peculiar abundance pattern of a \W Bootis star as previously suggested. We investigate the effects of rotation on the deduced abundances and show that the dominant ionization states are only slightly affected compared to analyses using non-rotating models. We argue that the rapid rotation requires the star be fully mixed. The composition leads to masses and particularly ages that are quite different compared to what are usually assumed.Comment: 16 pages, 4 figures, accepted by Ap

A Road Map for the Exploration of Neighboring Planetary Systems (ExNPS)

A brown dwarf star having only 20-50 times the mass of Jupiter is located below and to the left of the bright star GL 229 in this image from the Hubble Space Telescope. At the 19 light year distance to GL 229, the 7.7-arcsec separation between the star and the brown dwarf corresponds to roughly the separation between Pluto and the Sun in our Solar System. The goal of the program described in this report is to detect and characterize Earth-like planets around nearby stars where conditions suitable for life might be found. For a star like the Sun located 30 light years away, the appropriate star-planet separation would be almost 100 times closer than seen here for GL 229B

POD\u2013Galerkin reduced order methods for combined Navier\u2013Stokes transport equations based on a hybrid FV-FE solver

The purpose of this work is to introduce a novel POD\u2013Galerkin strategy for the semi-implicit hybrid high order finite volume/finite element solver introduced in Berm\ufadez et al. (2014) and Busto et al. (2018). The interest is into the incompressible Navier\u2013Stokes equations coupled with an additional transport equation. The full order model employed in this article makes use of staggered meshes. This feature will be conveyed to the reduced order model leading to the definition of reduced basis spaces in both meshes. The reduced order model presented herein accounts for velocity, pressure, and a transport-related variable. The pressure term at both the full order and the reduced order level is reconstructed making use of a projection method. More precisely, a Poisson equation for pressure is considered within the reduced order model. Results are verified against three-dimensional manufactured test cases. Moreover a modified version of the classical cavity test benchmark including the transport of a species is analysed

Finite volume POD-Galerkin stabilised reduced order methods for the parametrised incompressible Navier\u2013Stokes equations

In this work a stabilised and reduced Galerkin projection of the incompressible unsteady Navier\u2013Stokes equations for moderate Reynolds number is presented. The full-order model, on which the Galerkin projection is applied, is based on a finite volumes approximation. The reduced basis spaces are constructed with a POD approach. Two different pressure stabilisation strategies are proposed and compared: the former one is based on the supremizer enrichment of the velocity space, and the latter one is based on a pressure Poisson equation approach

Serine Protease Autotransporters of Enterobacteriaceae (SPATEs): Biogenesis and Function

Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) constitute a large family of proteases secreted by Escherichia coli and Shigella. SPATEs exhibit two distinct proteolytic activities. First, a C-terminal catalytic site triggers an intra-molecular cleavage that releases the N-terminal portion of these proteins in the extracellular medium. Second, the secreted N-terminal domains of SPATEs are themselves proteases; each contains a canonical serine-protease catalytic site. Some of these secreted proteases are toxins, eliciting various effects on mammalian cells. Here, we discuss the biogenesis of SPATEs and their function as toxins

Diffusion of a soluble protein, photoactivatable GFP, through a sensory cilium

Transport of proteins to and from cilia is crucial for normal cell function and survival, and interruption of transport has been implicated in degenerative and neoplastic diseases. It has been hypothesized that the ciliary axoneme and structures adjacent to and including the basal bodies of cilia impose selective barriers to the movement of proteins into and out of the cilium. To examine this hypothesis, using confocal and multiphoton microscopy we determined the mobility of the highly soluble photoactivatable green fluorescent protein (PAGFP) in the connecting cilium (CC) of live Xenopus retinal rod photoreceptors, and in the contiguous subcellular compartments bridged by the CC, the inner segment (IS) and the outer segment (OS). The estimated axial diffusion coefficients are DCC = 2.8 ± 0.3, DIS = 5.2 ± 0.6, and DOS = 0.079 ± 0.009 µm2 s−1. The results establish that the CC does not pose a major barrier to protein diffusion within the rod cell. However, the results also reveal that axial diffusion in each of the rod’s compartments is substantially retarded relative to aqueous solution: the axial diffusion of PAGFP was retarded ∼18-, 32- and 1,000-fold in the IS, CC, and OS, respectively, with ∼20-fold of the reduction in the OS attributable to tortuosity imposed by the lamellar disc membranes. Previous investigation of PAGFP diffusion in passed, spherical Chinese hamster ovary cells yielded DCHO = 20 µm2 s−1, and estimating cytoplasmic viscosity as Daq/DCHO = 4.5, the residual 3- to 10-fold reduction in PAGFP diffusion is ascribed to sub-optical resolution structures in the IS, CC, and OS compartments

Acute physiological stress down-regulates mRNA expressions of growth-related genes in coho salmon

Growth and development in fish are regulated to a major extent by growth-related factors, such as liver-derived insulin-like growth factor (IGF) -1 in response to pituitary-secreted growth hormone (GH) binding to the GH receptor (GHR). Here, we report on the changes in the expressions of gh, ghr, and igf1 genes and the circulating levels of GH and IGF-1 proteins in juvenile coho salmon (Oncorhynchus kisutch) in response to handling as an acute physiological stressor. Plasma GH levels were not significantly different between stressed fish and prestressed control. Plasma IGF-1 concentrations in stressed fish 1.5 h post-stress were the same as in control fish, but levels in stressed fish decreased significantly 16 h post-stress. Real-time quantitative PCR (qPCR) analysis showed that ghr mRNA levels in pituitary, liver, and muscle decreased gradually in response to the stressor. After exposure to stress, hepatic igf1 expression transiently increased, whereas levels decreased 16 h post-stress. On the other hand, the pituitary gh mRNA level did not change in response to the stressor. These observations indicate that expression of gh, ghr, and igf1 responded differently to stress. Our results show that acute physiological stress can mainly down-regulate the expressions of growth-related genes in coho salmon in vivo. This study also suggests that a relationship between the neuroendocrine stress response and growth-related factors exists in fish.Peer reviewed: YesNRC publication: Ye

Intraflagellar transport molecules in ciliary and nonciliary cells of the retina

IFT proteins are differentially localized in photoreceptor cilia, including within the inner segment, and some are shown to function in trafficking in nonciliated retinal neurons

Expanding the knowledge about Leishmania species in wild mammals and dogs in the Brazilian savannah

Background: Wild, synanthropic and domestic mammals act as hosts and/or reservoirs of several Leishmania spp. Studies on possible reservoirs of Leishmania in different areas are fundamental to understand host-parasite interactions and develop strategies for the surveillance and control of leishmaniasis. In the present study, we evaluated the Leishmania spp. occurrence in mammals in two conservation units and their surroundings in Brasília, Federal District (FD), Brazil. Methods: Small mammals were captured in Brasília National Park (BNP) and Contagem Biological Reserve (CBR) and dogs were sampled in residential areas in their vicinity. Skin and blood samples were evaluated by PCR using different molecular markers (D7 24Sα rRNA and rDNA ITS1). Leishmania species were identified by sequencing of PCR products. Dog blood samples were subjected to the rapid immunochromatographic test (DPP) for detection of anti-Leishmania infantum antibodies. Results: 179 wild mammals were studied and 20.1% had Leishmania DNA successfully detected in at least one sample. Six mammal species were considered infected: Clyomys laticeps, Necromys lasiurus, Nectomys rattus, Rhipidomys macrurus, Didelphis albiventris and Gracilinanus agilis. No significant difference, comparing the proportion of individuals with Leishmania spp., was observed between the sampled areas and wild mammal species. Most of the positive samples were collected from the rodent N. lasiurus, infected by L. amazonensis or L. braziliensis. Moreover, infections by Trypanosoma spp. were detected in N. lasiurus and G. agilis. All 19 dog samples were positive by DPP; however, only three (15.8%) were confirmed by PCR assays. DNA sequences of ITS1 dog amplicons showed 100% identity with L. infantum sequence. Conclusions: The results suggest the participation of six species of wild mammals in the enzootic transmission of Leishmania spp. in FD. This is the first report of L. amazonensis in N. lasiurus