726 research outputs found
Observation of the first gravitational microlensing event in a sparse stellar field : the Tago event
We report the observation of the first gravitational microlensing event in a
sparse stellar field, involving the brightest (V=11.4 mag) andclosest (~ 1 kpc)
source star to date. This event was discovered by an amateurastronomer, A.
Tago, on 2006 October 31 as a transient brightening, by ~4.5 mag during a ~15
day period, of a normal A-type star (GSC 3656-1328) in the Cassiopeia
constellation. Analysis of both spectroscopic observations and the light curve
indicates that this event was caused by gravitational microlensing rather than
an intrinsically variable star. Discovery of this single event over a 30 year
period is roughly consistent with the expected microlensing rate for the whole
sky down to V = 12 mag stars. However, the probability for finding events with
such a high magnification (~ 50) is much smaller, by a factor ~1/50, which
implies that the true event rate may be higher than expected. This discovery
indicates the potential of all sky variability surveys, employing frequent
sampling by telescopes with small apertures and wide fields of view, for
finding such rare transient events, and using the observations to explore
galactic disk structure and search for exo-planets.Comment: 13 pages, 2 tables, 3 figures, accepted by Ap
Improving Vaccine-Induced Immunity: Can Baseline Predict Outcome?
Immune signatures measured at baseline and immediately prior to vaccination may predict the immune response to vaccination. Such pre-vaccine assessment might allow not only population-based, but also more personalized vaccination strategies ('precision vaccination'). If baseline immune signatures are predictive, the underlying mechanism they reflect
may also determine vaccination outcome. Thus, baseline signatures might contribute to identifying interventional targets to be modulated prior to vaccination in order to improve vaccination responses. This concept has the potential to transform vaccination strategies and usher in a new approach to improve global health
Chandra Observations of 3C Radio Sources with z<0.3: Nuclei, Diffuse Emission, Jets and Hotspots
We report on our Chandra Cycle 9 program to observe half of the 60
(unobserved by Chandra) 3C radio sources at z<0.3 for 8 ksec each. Here we give
the basic data: the X-ray intensity of the nuclei and any features associated
with radio structures such as hot spots and knots in jets. We have measured
fluxes in soft, medium and hard bands and are thus able to isolate sources with
significant intrinsic column density. For the stronger nuclei, we have applied
the standard spectral analysis which provides the best fit values of X-ray
spectral index and column density. We find evidence for intrinsic absorption
exceeding a column density of 10^{22} cm^{-2} for one third of our sources.Comment: 12 pages, 37 figures (the complete version of the paper with all
figures is available on line, see appendix for details), ApJ accepte
Large-scale gas disk around the radio galaxy Coma A
We present WSRT and VLA radio observations of the neutral hydrogen in the
radio galaxy Coma A. We detect extended HI absorption against both radio lobes
of Coma A, at distances of about 30 kpc from the centre. Coma A is the first
radio galaxy in which HI is seen in absorption at such large distances from the
nucleus. The match between the velocities of the neutral hydrogen and those of
the extended ionized gas suggests that they are part of the same disk-like
structure of at least 60 kpc in diameter. Most likely, this gas disk is partly
ionised by the bulk motion of the radio lobes expanding into it. The gas mass
of this disk is at least 10^9 Msun. The relatively regular structure of the gas
disk suggests that a merger occurred involving at least one large gas-rich
galaxy, at least a few times 10^8 yr ago.Comment: Accepted for publication in A&A, 8 pages, 8 figure
Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients: another piece of the puzzle
Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN
2009ip-like events are characterized by a long-lasting phase of erratic
variability which ends with two luminous outbursts a few weeks apart. The
second outburst is significantly more luminous (about 3 mag) than the first. In
the case of SN 2016bdu, the first outburst (Event A) reached an absolute
magnitude M(r) ~ -15.3 mag, while the second one (Event B) occurred over one
month later and reached M(r) ~ -18 mag. By inspecting archival data, a faint
source at the position of SN 2016bdu is detectable several times in the past
few years. We interpret these detections as signatures of a phase of erratic
variability, similar to that experienced by SN 2009ip between 2008 and
mid-2012, and resembling the currently observed variability of the luminous
blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu
during the second peak initially shows features typical of a SN IIn. One month
after the Event B maximum, the spectra develop broad Balmer lines with P Cygni
profiles and broad metal features. At these late phases, the spectra resemble
those of a typical Type II SN. All members of this SN 2009ip-like group are
remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a
terminal SN explosion is supported by the disappearance of the progenitor star.
The similarity with SN 2005gl suggests that all members of this family may
finally explode as genuine SNe, although the unequivocal detection of
nucleosynthesised elements in their nebular spectra is still missing.Comment: Submitted to MNRAS on April 10, 2017; re-submitted on June 23
including suggestions from the referee. 24 pages, 12 figures, 5 table
SDSS J162520.29+120308.7 – a new SU Ursae Majoris star in the period gap
We report results of an extensive world-wide observing campaign devoted to the recently discovered dwarf nova
SDSS J162520.29+120308.7 (SDSS J1625). The data were obtained during the July 2010 eruption of the star and in August and
September 2010 when the object was in quiescence. During the July 2010 superoutburst, SDSS J1625 clearly displayed superhumps
with a mean period of Psh = 0.095942(17) days (138.16 ± 0.02 min) and a maximum amplitude reaching almost 0.4 mag. The superhump
period was not stable, decreasing very rapidly at a rate of ˙P = −1.63(14) × 10−3 at the beginning of the superoutburst and
increasing at a rate of ˙P = 2.81(20) × 10−4 in the middle phase. At the end of the superoutburst, it stabilized around the value of
Psh = 0.09531(5) day.
During the first twelve hours of the superoutburst, a low-amplitude double wave modulation was observed whose properties are
almost identical to early superhumps observed in WZ Sge stars. The period of early superhumps, the period of modulations observed
temporarily in quiescence, and the period derived from radial velocity variations are the same within measurement errors, allowing
us to estimate the most probable orbital period of the binary to be Porb = 0.09111(15) days (131.20 ± 0.22 min). This value clearly
indicates that SDSS J1625 is another dwarf nova in the period gap. Knowledge of the orbital and superhump periods allows us to
estimate the mass ratio of the system to be q ≈ 0.25. This high value poses serious problems for both the thermal and tidal instability
(TTI) model describing the behaviour of dwarf novae and for some models explaining the origin of early superhumps
Design of Cationic Multi-Walled Carbon Nanotubes as Efficient siRNA Vectors for Lung Cancer Xenograft Eradication
Polo-Like Kinase (PLK1) has been identified as a potential target in cancer gene therapy via chemical or genetic inhibitory approaches. The biomedical applications of chemically functionalized carbon nanotubes (f-CNTs) in cancer therapy have been studied due to their ability to efficiently deliver siRNA intracellularly. In this study, we established the capacity of cationic MWNT-NH3+ to deliver the apoptotic siRNA against PLK1 (siPLK1) in Calu6 tumor xenografts by direct intratumoural injections. A direct comparison with cationic liposomes was made. This study validates the PLK1 gene as a potential target in cancer gene therapy including lung cancer, as demonstrated by the therapeutic efficacy of siPLK1:MWNT-NH3+ complexes and their ability to significantly improve animal survival. Biological analysis of the siPLK1:MWNT-NH3+ treated tumors by RT-PCR and Western blot, in addition to TUNEL staining confirmed the biological functionality of the siRNA intratumourally, suggesting that tumor eradication was due to PLK1 knockdown. Furthermore, by using a fluorescently labelled, non-coding siRNA sequence complexed with MWNT-NH3+, we established for the first time that the improved therapeutic efficacy observed in f-CNT-based siRNA delivery is directly proportional to the enhanced siRNA retention in the solid tumor and subsequent uptake by tumor cells after local administration in vivo
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