764 research outputs found
Hot Stars With Cool Companions
Young intermediate-mass stars have become high-priority targets for
direct-imaging planet searches following the recent discoveries of planets
orbiting e.g. HR 8799 and Beta Pictoris. Close stellar companions to these
stars can affect the formation and orbital evolution of any planets, and so a
census of the multiplicity properties of nearby intermediate mass stars is
needed. Additionally, the multiplicity can help constrain the important binary
star formation physics. We report initial results from a spectroscopic survey
of 400 nearby A- and B-type stars. We search for companions by
cross-correlating high resolution and high signal-to-noise ratio echelle
spectra of the targets stars against model spectra for F- to M-type stars. We
have so far found 18 new candidate companions, and have detected the spectral
lines of the secondary in 4 known spectroscopic binary systems. We present the
distribution of mass-ratios for close companions, and find that it differs from
the distribution for wide ( AU) intermediate-mass binaries, which may
indicate a different formation mechanism for the two populations.Comment: Submitted as part of the 18th Cambridge Workshop on Cool Stars,
Stellar Systems, and the Sun Proceedings of Lowell Observatory (9-13 June
2014
Correcting For Telluric Absorption: Methods, Case Studies, And Release Of The TelFit Code
Ground-based astronomical spectra are contaminated by the Earth's atmosphere to varying degrees in all spectral regions. We present a Python code that can accurately fit a model to the telluric absorption spectrum present in astronomical data, with residuals of similar to 3%-5% of the continuum for moderately strong lines. We demonstrate the quality of the correction by fitting the telluric spectrum in a nearly featureless A0V star, HIP 20264, as well as to a series of dwarf M star spectra near the 819 nm sodium doublet. We directly compare the results to an empirical telluric correction of HIP 20264 and find that our model-fitting procedure is at least as good and sometimes more accurate. The telluric correction code, which we make freely available to the astronomical community, can be used as a replacement for telluric standard star observations for many purposes.UT Austin Hutchinson fellowshipUniversity of TexasAstronom
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Diencephalic-mesencephalic Junction Dysplasia: A Case Report and Overview of What is Known so far
Background: Diencephalic-mesencephalic junction dysplasia (DMJD) is a rare and recently newly described forebrain-midbrain malformation involving the upper aspect of the brainstem and resulting in an abnormal regionalization of the diencephalon and mesencephalon level. The fingerprint of DMJD is the pathognomonic butterfly-like appearance of the midbrain seen on the axial plane of brain magnetic resonance imaging (MRI). Initially, only two types of diencephalon-mesencephalon continuity were defined: type A describes the continuity of the hypothalamus with the mesencephalon, and type B a parenchymal band between the thalamus and the superior surface of the midbrain. However, DMJD classification continues to expand, and recently, type C was described as showing a complete continuity of the thalamus and midbrain. In this paper, we refer to mesencephalon and midbrain as the anatomical marker of the topmost part of the brainstem, and those terms are used interchangeably in the text.
Methodology: PubMed database search for the exact words “diencephalic-mesencephalic junction dysplasia” and “DMJD” yielded 12 relevant publications. A showcase of an original rare type C DMJD was performed.
Objective: The purpose of this article is to present a brief comprehensive illustration /elucidation of the physiopathology of neural tube regionalization to facilitate the understanding of DMJD malformation; to present an updated overview of recent publications involving imaging findings, genetics, and clinical concerns; and to show an original fetal case of type C DJMD. The aim is to increase awareness of DMJD and strengthen clinical suspicion, especially since early diagnosis is primarily based on imaging
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This article includes an overview of the Sci-Tech Division sessions that will take place at the 2011 SLA Conference in Philadelphia, as well as a listing of new Science-Technology Division members and a call for candidates for the Science-Technology Division Board
Vaccination directed against the human endogenous retrovirus-K envelope protein inhibits tumor growth in a murine model system
Human endogenous retrovirus (HERV) genomes are chromosomally integrated in all cells of an individual. They are normally transcriptionally silenced and transmitted only vertically. Enhanced expression of HERV-K accompanied by the emergence of anti-HERV-K-directed immune responses has been observed in tumor patients and HIV-infected individuals. As HERV-K is usually not expressed and immunological tolerance development is unlikely, it is an appropriate target for the development of immunotherapies. We generated a recombinant vaccinia virus (MVA-HKenv) expressing the HERV-K envelope glycoprotein (ENV), based on the modified vaccinia virus Ankara (MVA), and established an animal model to test its vaccination efficacy. Murine renal carcinoma cells (Renca) were genetically altered to express E. coli beta-galactosidase (RLZ cells) or the HERV-K ENV gene (RLZ-HKenv cells). Intravenous injection of RLZ-HKenv cells into syngenic BALB/c mice led to the formation of pulmonary metastases, which were detectable by X-gal staining. A single vaccination of tumor-bearing mice with MVA-HKenv drastically reduced the number of pulmonary RLZ-HKenv tumor nodules compared to vaccination with wild-type MVA. Prophylactic vaccination of mice with MVA-HKenv precluded the formation of RLZ-HKenv tumor nodules, whereas wild-type MVA-vaccinated animals succumbed to metastasis. Protection from tumor formation correlated with enhanced HERV-K ENV-specific killing activity of splenocytes. These data demonstrate for the first time that HERV-K ENV is a useful target for vaccine development and might offer new treatment opportunities for diverse types of cancer
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