3,585 research outputs found
VLBA 24 and 43 GHz observations of massive binary black hole candidate PKS 1155+251
PKS 1155+251 is a radio-loud quasar source at z=0.203. Observations using
very long baseline interferometry (VLBI) at ~2, 5, 8 and 15 GHz show that the
structure of the radio source is quite complicated on parsec scales and that
the outer hot spots are apparently undergoing a significant contraction.
Because these results cannot be fully explained based on the compact symmetric
object (CSO) scenario with a radio core located between the northern and
southern complexes, we made observations with the Very Long Baseline Array
(VLBA) at 24 and 43 GHz to search for compact substructures and alternative
interpretations. The results show that the radio core revealed in the previous
VLBI observations remains compact with a flat spectrum in our
sub-milli-arcsecond--resolution images; the northern lobe emission becomes
faint at 24 GHz and is mostly resolving out at 43 GHz; the southern complex is
more bright but has been resolved into the brightest southern-end (S1) and jet
or tail alike components westwards. Explaining the southern components aligned
westward with a standard CSO scenario alone remains a challenge. As for the
flatter spectral index of the southern-end component S1 between 24 and 43 GHz
in our observations and the significant 15 GHz VLBA flux variability of S1, an
alternative scenario is that the southern complex may be powered by a secondary
black hole residing at S1. But more sensitive and high-resolution VLBI
monitoring is required to discriminate the CSO and the binary black hole
scenarios.Comment: 7 pages, 3 figures, accepted by MNRA
Electronic structure of S-C6H5 self-assembled monolayers on Cu(111) and Au(111) substrates
We use first principles density functional theory to calculate the electronic
structure of the phenylthiolate (S-CH) self-assembled monolayer (SAM)
on Cu(111) and Au(111) substrates. We find significant lateral dispersion of
the SAM molecular states and discuss its implications for transport properties
of the molecular wire array. We calculate the two photon photoemission spectra
and the work function of the SAM on Cu(111) and compare them with the available
experimental data. Our results are used to discuss assignments of the observed
spectral data and yield predictions for new electronic states due to the
monolayer not yet accessed experimentally.Comment: 7 pages, 7 figure
Enhanced Management of Personal Astronomical Data with FITSManager
Although the roles of data centers and computing centers are becoming more
and more important, and on-line research is becoming the mainstream for
astronomy, individual research based on locally hosted data is still very
common. With the increase of personal storage capacity, it is easy to find
hundreds to thousands of FITS files in the personal computer of an
astrophysicist. Because Flexible Image Transport System (FITS) is a
professional data format initiated by astronomers and used mainly in the small
community, data management toolkits for FITS files are very few. Astronomers
need a powerful tool to help them manage their local astronomical data.
Although Virtual Observatory (VO) is a network oriented astronomical research
environment, its applications and related technologies provide useful solutions
to enhance the management and utilization of astronomical data hosted in an
astronomer's personal computer. FITSManager is such a tool to provide
astronomers an efficient management and utilization of their local data,
bringing VO to astronomers in a seamless and transparent way. FITSManager
provides fruitful functions for FITS file management, like thumbnail, preview,
type dependent icons, header keyword indexing and search, collaborated working
with other tools and online services, and so on. The development of the
FITSManager is an effort to fill the gap between management and analysis of
astronomical data.Comment: 12 pages, 9 figures, Accepted for publication in New Astronom
Ruling out GeV thermal relic annihilating dark matter by radio observation of the Andromeda galaxy
In the past few years, some studies claimed that annihilating dark matter
with mass GeV can explain the GeV gamma-ray excess in our Galaxy.
However, recent analyses of the Fermi-LAT and radio observational data rule out
the possibility of the thermal relic annihilating dark matter with mass GeV for some popular annihilation channels. By using the new observed
radio data of the Andromeda galaxy, we rule out the existence of
GeV thermal relic annihilating dark matter for ten annihilation channels. The
lower limits of annihilating dark matter mass are improved to larger than 330
GeV for the most conservative case, which is a few times larger than the
current best constraints. Moreover, these limits strongly disfavor the
benchmark model of weakly interacting massive particle (WIMP) produced through
the thermal freeze-out mechanism.Comment: Accepted in Ap
Nonsurgical periodontal treatment reduced aortic inflammation in ApoE−/− mice with periodontitis
Nonlinear current-induced forces in Si atomic wires
We report first-principles calculations of current-induced forces in Si
atomic wires as a function of bias and wire length. We find that these forces
are strongly nonlinear as a function of bias due to the competition between the
force originating from the scattering states and the force due to bound states.
We also find that the average force in the wire is larger the shorter the wire,
suggesting that atomic wires are more difficult to break under current flow
with increasing length. The last finding is in agreement with recent
experimental data.Comment: 4 figure
Single nucleotide polymorphisms affect both cis- and trans-eQTLs
AbstractSingle nucleotide polymorphisms (SNPs) between microarray probes and RNA targets can affect the performance of expression array by weakening the hybridization. In this paper, we examined the effect of the SNPs on Affymetrix GeneChip probe set summaries and the expression quantitative trait loci (eQTL) mapping results in two eQTL datasets, one from mouse and one from human. We showed that removing SNP-containing probes significantly changed the probe set summaries and the more SNP-containing probes we removed the greater the change. Comparison of the eQTL mapping results between with and without SNP-containing probes showed that less than 70% of the significant eQTL peaks were concordant regardless of the significance threshold. These results indicate that SNPs do affect both probe set summaries and eQTLs (both cis and trans), thus SNP-containing probes should be filtered out to improve the performance of eQTL mapping
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