1,125 research outputs found
A Five-year Spectroscopic and Photometric Campaign on the Prototypical alpha Cygni Variable and A-type Supergiant Star Deneb
Deneb is often considered the prototypical A-type supergiant, and is one of
the visually most luminous stars in the Galaxy. A-type supergiants are
potential extragalactic distance indicators, but the variability of these stars
needs to be better characterized before this technique can be considered
reliable. We analyzed 339 high resolution echelle spectra of Deneb obtained
over the five-year span of 1997 through 2001 as well as 370 Stromgren
photometric measurements obtained during the same time frame. Our spectroscopic
analysis included dynamical spectra of the H-alpha profile, H-alpha equivalent
widths, and radial velocities measured from Si II 6347, 6371. Time-series
analysis reveals no obvious cyclic behavior that proceeds through multiple
observing seasons, although we found a suspected 40 day period in two,
non-consecutive observing seasons. Some correlations are found between
photometric and radial velocity data sets, and suggest radial pulsations at two
epochs. No correlation is found between the variability of the H-alpha profiles
and that of the radial velocities or the photometry. Lucy (1976) found evidence
that Deneb was a long period single-lined spectroscopic binary star, but our
data set shows no evidence for radial velocity variations caused by a binary
companion.Comment: 49 pages, 9 figures, 5 tables, accepted for publication in the
Astronomical Journa
Identification of clinical infections of Leishmania imported into Australia: Revising speciation with polymerase chain reaction-RFLP of the kinetoplast maxicircle
Copyright © 2019 by The American Society of Tropical Medicine and Hygiene. Leishmaniasis is a vector-borne disease caused by protozoan parasites of the Leishmania genus. In Australia, leishmaniasis is an imported disease that is presenting itself at increased rates because of international travel, the influx of immigrants, and deployment of military operations to endemic regions. Although Leishmania species are morphologically indistinguishable, there is a strong correlation between some causative species of leishmaniasis and the subsequent response to the treatments available and patient outcome. Consequently, identification of the infective species is imperative as misidentification can result in the administering of an ineffective drug. The aim of this study was to develop a simple diagnostic tool with high sensitivity and specificity, which is capable of detecting the presence of the parasite and accurately differentiating the causative species in question. Using the advantageous properties of the maxi-circle kinetoplast DNA, a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) targeting the ND7 gene was developed for the analysis of imported cases of human leishmaniasis in Australia. Designed as a dual analysis, concurrent PCR of Leishmania maxi-circle DNA and digestion with two separate enzymes (NlaIII and HpyCH4IV), this study provides an appraisal on 24 imported cases of leishmaniasis between 2008 and 2017. Five Leishmania species were reported, with members of the Viannia subgenus being the most common. The implementation of novel diagnostic procedures for leishmaniasis such as the one reported here is needed to establish a gold standard practice for the diagnosis and treatment of leishmaniasis
First Stellar Abundances in the Dwarf Irregular Galaxy Sextans A
We present the abundance analyses of three isolated A-type supergiant stars
in the dwarf irregular galaxy Sextans A from high-resolution spectra the UVES
spectrograph at the VLT. Detailed model atmosphere analyses have been used to
determine the stellar atmospheric parameters and the elemental abundances of
the stars. The mean iron group abundance was determined from these three stars
to be [(FeII,CrII)/H]=-0.99+/-0.04+/-0.06. This is the first determination of
the present-day iron group abundances in Sextans A. These three stars now
represent the most metal-poor massive stars for which detailed abundance
analyses have been carried out. The mean stellar alpha element abundance was
determined from the alpha element magnesium as
[alpha(MgI)/H]=-1.09+/-0.02+/-0.19. This is in excellent agreement with the
nebular alpha element abundances as determined from oxygen in the H II regions.
These results are consistent from star-to-star with no significant spatial
variations over a length of 0.8 kpc in Sextans A. This supports the nebular
abundance studies of dwarf irregular galaxies, where homogeneous oxygen
abundances are found throughout, and argues against in situ enrichment. The
alpha/Fe abundance ratio is [alpha(MgI)/FeII,CrII]=-0.11+/-0.02+/-0.10, which
is consistent with the solar ratio. This is consistent with the results from
A-supergiant analyses in other Local Group dwarf irregular galaxies but in
stark contrast with the high [alpha/Fe] results from metal-poor stars in the
Galaxy, and is most clearly seen from these three stars in Sextans A because of
their lower metallicities. The low [alpha/Fe] ratios are consistent with the
slow chemical evolution expected for dwarf galaxies from analyses of their
stellar populations.Comment: 40 pages, 8 figures, accepted for publication in A
IFNα and IFNγ Impede Marek’s Disease Progression
Marek’s disease virus (MDV) is an alphaherpesvirus that causes Marek’s disease, a malignant lymphoproliferative disease of domestic chickens. While MDV vaccines protect animals from clinical disease, they do not provide sterilizing immunity and allow field strains to circulate and evolve in vaccinated flocks. Therefore, there is a need for improved vaccines and for a better understanding of innate and adaptive immune responses against MDV infections. Interferons (IFNs) play important roles in the innate immune defenses against viruses and induce upregulation of a cellular antiviral state. In this report, we quantified the potent antiviral effect of IFNα and IFNγ against MDV infections in vitro. Moreover, we demonstrate that both cytokines can delay Marek’s disease onset and progression in vivo. Additionally, blocking of endogenous IFNα using a specific monoclonal antibody, in turn, accelerated disease. In summary, our data reveal the effects of IFNα and IFNγ on MDV infection and improve our understanding of innate immune responses against this oncogenic virus
Tomographic readout of an opto-mechanical interferometer
The quantum state of light changes its nature when being reflected off a
mechanical oscillator due to the latter's susceptibility to radiation pressure.
As a result, a coherent state can transform into a squeezed state and can get
entangled with the motion of the oscillator. The complete tomographic
reconstruction of the state of light requires the ability to readout arbitrary
quadratures. Here we demonstrate such a readout by applying a balanced homodyne
detector to an interferometric position measurement of a thermally excited
high-Q silicon nitride membrane in a Michelson-Sagnac interferometer. A readout
noise of \unit{1.9 \cdot 10^{-16}}{\metre/\sqrt{\hertz}} around the
membrane's fundamental oscillation mode at \unit{133}{\kilo\hertz} has been
achieved, going below the peak value of the standard quantum limit by a factor
of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a
rather broad frequency range around the mechanical resonance.Comment: 7 pages, 5 figure
The complete coding region of the maxicircle as a superior phylogenetic marker for exploring evolutionary relationships between members of the Leishmaniinae
© 2019 Elsevier B.V. The mitochondrial DNA (mtDNA) is a potentially valuable phylogenetic marker given its presence across all eukaryotic taxa and its relative conservation in structure and sequence. In trypanosomatids, a homologue of the mtDNA referred to as the maxicircle DNA, is located within a specialised structure in the single mitochondrion of the trypanosomatids called the kinetoplast; a high molecular weight network of DNA composed of thousands of catenated minicircles and a smaller number of larger maxicircles. Unique to the kinetoplastid protists, the maxicircle component of this complex network could represent a desirable target for taxonomic inquiry that may also facilitate exploration of the evolutionary history of this important group of parasites. The aim of this study was to investigate the phylogenetic value of the trypanosomatid maxicircle for these applications. Maxicircle sequences were obtained either by assembling raw sequence data publicly accessible in online databases (i.e., NCBI), or by amplification of novel maxicircle sequences from trypanosomatid DNA using long-range (LR) PCR with subsequent Illumina sequencing. This procedure facilitated the generation of nearly complete maxicircle sequences (i.e., excluding the divergent region) for numerous dixenous and monoxenous trypanosomatid species. Annotation of each maxicircle sequence confirmed that their structure was conserved across all taxa examined. Phylogenetic analyses confirmed that Z. australiensis showed a greater genetic relatedness with the dixenous trypanosomatids of the genera Leishmania and Endotrypanum, as opposed to members of the monoxenous genera Crithidia and Leptomonas. Additionally, molecular clock analysis supported that the dixenous Leishmaniinae appeared approximately 75 million years ago during the breakup of Gondwana. In line with previous studies, our results support the Supercontinents hypothesis regarding the origin of dixenous Leishmaniinae. Ultimately, we demonstrate that the maxicircle represents an excellent phylogenetic marker for studying the evolutionary history of trypanosomatids, resulting in trees with very high bootstrap support values
A Special Issue on Marek’s Disease Virus - The Editors’ View
Marek’s disease virus (MDV), an Alphaherpesvirus belonging to the genus Mardivirus, causes T cell lymphomas in chickens and remains one of the greatest threats to poultry production worldwide. While losses caused by Marek’s disease have been reduced through live-attenuated vaccines, field strains have increased in virulence over recent decades. MDV research has led to a profound understanding of virus-induced pathogenesis and tumor development [1,2,3]. Our goal with this Microorganisms Special Issue on Marek’s disease virus was to collect manuscripts that would provide deeper insights into MDV infection, lytic replication, and latency in vitro and in vivo. Moreover, we assembled reports that provide novel data on pathogenesis, immune system interactions, as well as state-of-the-art concepts to identify approaches to control MDV infections. We were happy to edit seven research articles, three short communications, and a review article on these diverse aspects of MDV infections
The Transcriptional Landscape of Marek’s Disease Virus in Primary Chicken B Cells Reveals Novel Splice Variants and Genes
Marek’s disease virus (MDV) is an oncogenic alphaherpesvirus that infects chickens and poses a serious threat to poultry health. In infected animals, MDV efficiently replicates in B cells in various lymphoid organs. Despite many years of research, the viral transcriptome in primary target cells of MDV remained unknown. In this study, we uncovered the transcriptional landscape of the very virulent RB1B strain and the attenuated CVI988/Rispens vaccine strain in primary chicken B cells using high-throughput RNA-sequencing. Our data confirmed the expression of known genes, but also identified a novel spliced MDV gene in the unique short region of the genome. Furthermore, de novo transcriptome assembly revealed extensive splicing of viral genes resulting in coding and non-coding RNA transcripts. A novel splicing isoform of MDV UL15 could also be confirmed by mass spectrometry and RT-PCR. In addition, we could demonstrate that the associated transcriptional motifs are highly conserved and closely resembled those of the host transcriptional machinery. Taken together, our data allow a comprehensive re-annotation of the MDV genome with novel genes and splice variants that could be targeted in further research on MDV replication and tumorigenesis
The Stellar Parameters and Evolutionary State of the Primary in the d'-Symbiotic System StH\alpha190
We report on a high-resolution, spectroscopic stellar parameter and abundance
analysis of a d' symbiotic star: the yellow component of StH\alpha190. This
star has recently been discovered, and confirmed here, to be a rapidly rotating
(vsini=100 km/s) subgiant, or giant, that exhibits radial-velocity variations
of probably at least 40 km/s, indicating the presence of a companion (a white
dwarf star). It is found that the cool stellar component has Teff=5300K and log
g=3.0. The iron and calcium abundances are close to solar, however, barium is
overabundant, relative to Fe and Ca, by about +0.5 dex. The barium enhancement
reflects mass-transfer of s-process enriched material when the current white
dwarf was an asymptotic giant branch (AGB) star. The past and future evolution
of this binary system depends critically on its current orbital period, which
is not yet known. Concerted and frequent radial-velocity measurements are
needed to provide crucial physical constraints to this d' symbiotic system.Comment: 9 pages, 1 table, 3 figures. In press to Astrophysical Journal
Letter
Multi-periodic photospheric pulsations and connected wind structures in HD64760
We report on the results of an extended optical spectroscopic monitoring
campaign on the early-type B supergiant HD64760 (B0.5Ib) designed to probe the
deep-seated origin of spatial wind structure. This new study is based on
high-resolution echelle spectra obtained with the FEROS instrument at ESO La
Silla. 279 spectra were collected over 10 consecutive nights in 2003. From the
period analysis of the line-profile variability of the photospheric lines we
identify three closely spaced periods around 4.810 hrs and a splitting of
+/-3%. The velocity - phase diagrams of the line-profile variations for the
distinct periods reveal characteristic prograde non-radial pulsation patterns
of high order corresponding to pulsation modes with l and m in the range 6-10.
The three pulsation modes have periods clearly shorter than the characteristic
pulsation time scale and show small horizontal velocity fields and hence are
identified as p-modes. The beating of the three pulsation modes leads to a
retrograde beat pattern with two regions of constructive interference
diametrically opposite on the stellar surface and a beat period of 162.8hrs
(6.8days). This beat pattern is directly observed in the spectroscopic time
series of the photospheric lines. The wind-sensitive lines display features of
enhanced emission, which appear to follow the maxima of the photospheric beat
pattern.Comment: 18 pages, 21 figures (reduced resolution
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