5,052 research outputs found
HI and OH absorption in the lensing galaxy of MG J0414+0534
We report the detection of \HI 21-cm absorption in the early-type
lensing galaxy towards MG J0414+0534 with the Green Bank Telescope. The
absorption, with total , is resolved into two strong components, probably due to the two
strongest lens components, which are separated by 0.4\arcsec. Unlike the other
three lenses which have been detected in \HI, J0414+0534 does not exhibit
strong OH absorption, giving a OH/\HI column density ratio of N_{\rm
OH}/N_{\rm HI}\lapp10^{-6} (for K, K and
). This underabundance of molecular gas may indicate
that the extreme optical--near-IR colour () along the line-of-sight
is not due to the lens. We therefore suggest that despite the strong upper
limits on molecular absorption at the quasar redshift, as traced by millimetre
lines, the extinction occurs primarily in the quasar host galaxy.Comment: Accepted by MNRAS Letters, 5 (and a bit) pages, 5 figure
Cosmological Bounds on Spatial Variations of Physical Constants
We derive strong observational limits on any possible large-scale spatial
variation in the values of physical 'constants' whose space-time evolution is
driven by a scalar field. The limits are imposed by the isotropy of the
microwave background on large angular scales in theories which describe space
and time variations in the fine structure constant, the electron-proton mass
ratio, and the Newtonian gravitational constant, G. Large-scale spatial
fluctuations in the fine structure constant are bounded by 2x10^-9 and
1.2x10^-8 in the BSBM and VSL theories respectively, fluctuations in the
electron-proton mass ratio by 9x10^-5 in the BM theory and fluctuations in G by
3.6x10^-10 in Brans-Dicke theory. These derived bounds are significantly
stronger than any obtainable by direct observations of astrophysical objects at
the present time.Comment: 13 pages, 1 table, typos corrected, refs added. Published versio
Relaxation at late stages in an entropy barrier model for glassy systems
The ground state dynamics of an entropy barrier model proposed recently for
describing relaxation of glassy systems is considered. At stages of evolution
the dynamics can be described by a simple variant of the Ehrenfest urn model.
Analytical expression for the relaxation times from an arbitrary state to the
ground state is derived. Upper and lower bounds for the relaxation times as a
function of system size are obtained.Comment: 9 pages no figures. to appear in J.Phys. A: Math. and Ge
High-dimensional quantum dynamics of adsorption and desorption of H at Cu(111)
We performed high-dimensional quantum dynamical calculations of the
dissociative adsorption and associative desorption of hydrogen on Cu(111). The
potential energy surface (PES) is obtained from density functional theory
calculations. Two regimes of dynamics are found, at low energies sticking is
determined by the minimum energy barrier, at high energies by the distribution
of barrier heights. Experimental results are well-reproduced qualitatively, but
some quantitative discrepancies are identified as well.Comment: 4 two column pages, revtex, 4 figures, to appear in Phys. Rev. Let
AI as a legal person
Abstract: The idea of the legal personhood of artificial intelligence (AI) — the idea that intelligent agents can have rights and incur obligations under the law— is controversial, and in fact is often dismissed out of hand: in this paper I will argue that, on the contrary, such legal personhood may be the next big challenge for our legal systems, and we need it to deal with the new kinds ofcomplexity introduced by AI. Furthermore, I argue that we already have experiences we can look: to this end we can draw on the reasoning applied to the legal personhood recognized for corporations and other nonhuman entities. In order to do this, I address some of the criticisms against ascribing legal personhood to AI. I also look at the Canadian and EU ethical guidelines so as to keep the development of AI within the framework of human values, and I show that an ascription of legal personhood to AI is consistent with them. I also address a few of the big issues involved in making the legal personhood of AI a reality.This paper is part of the project supported by the CONEX programme and has received funding from the Universidad Carlos III de Madrid, the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement N. 600371, el Ministerio de Economia, Industria y Competitividad (COFUND2014-51509), el Ministerio de Educacion, Cultura y Deporte (CEI-15-17) and Banco SantanderUniversidad Carlos III de Madrid (APC. Read & Publish Agreement CRUE-CSIC 2023
Hackflex: low cost Illumina sequencing library construction for high sample counts
ABSTRACT We developed Hackflex, a low-cost method for the production of Illumina-compatible sequencing libraries that allows up to 11 times more libraries for high-throughput Illumina sequencing to be generated at a fixed cost. We call this new method Hackflex. Quality of library preparation was tested by constructing libraries from E. coli MG1655 genomic DNA using either Hackflex, standard Nextera Flex or a variation of standard Nextera Flex in which the bead-linked transposase is diluted prior to use. We demonstrated that Hackflex can produce high quality libraries and yields a highly uniform coverage, equivalent to the standard Nextera Flex kit. Using Hackflex, we were able to achieve a per sample reagent cost of library prep of A6.50/sample. This method will allow researchers to construct more libraries within a given budget, thereby yielding more data and facilitating research programs where sequencing large numbers of libraries is beneficial
Hackflex: low-cost, high-throughput, Illumina Nextera Flex library construction.
We developed a low-cost method for the production of Illumina-compatible sequencing libraries that allows up to 14 times more libraries for high-throughput Illumina sequencing to be generated for the same cost. We call this new method Hackflex. The quality of library preparation was tested by constructing libraries from Escherichia coli MG1655 genomic DNA using either Hackflex, standard Nextera Flex (recently renamed as Illumina DNA Prep) or a variation of standard Nextera Flex in which the bead-linked transposase is diluted prior to use. In order to test the library quality for genomes with a higher and a lower G+C content, library construction methods were also tested on Pseudomonas aeruginosa PAO1 and Staphylococcus aureus ATCC 25923, respectively. We demonstrated that Hackflex can produce high-quality libraries and yields a highly uniform coverage, equivalent to the standard Nextera Flex kit. We show that strongly size-selected libraries produce sufficient yield and complexity to support de novo microbial genome assembly, and that assemblies of the large-insert libraries can be much more contiguous than standard libraries without strong size selection. We introduce a new set of sample barcodes that are distinct from standard Illumina barcodes, enabling Hackflex samples to be multiplexed with samples barcoded using standard Illumina kits. Using Hackflex, we were able to achieve a per-sample reagent cost for library prep of A5.60; UK £3.87, £1=A$1.87), which is 9.87 times lower than the standard Nextera Flex protocol at advertised retail price. An additional simple modification and further simplification of the protocol by omitting the wash step enables a further price reduction to reach an overall 14-fold cost saving. This method will allow researchers to construct more libraries within a given budget, thereby yielding more data and facilitating research programmes where sequencing large numbers of libraries is beneficial
Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio at z=0.89 toward PKS1830-211
We report the first extragalactic detection of chloronium (H2Cl+), in the
z=0.89 absorber in front of the lensed blazar PKS1830-211. The ion is detected
through its 1_11-0_00 line along two independent lines of sight toward the
North-East and South-West images of the blazar. The relative abundance of H2Cl+
is significantly higher (by a factor ~7) in the NE line of sight, which has a
lower H2/H fraction, indicating that H2Cl+ preferably traces the diffuse gas
component. From the ratio of the H2^35Cl+ and H2^37Cl+ absorptions toward the
SW image, we measure a 35Cl/37Cl isotopic ratio of 3.1 (-0.2; +0.3) at z=0.89,
similar to that observed in the Galaxy and the solar system.Comment: Accepted for publication in A&A Lette
Probing the jet base of the blazar PKS1830-211 from the chromatic variability of its lensed images. Serendipitous ALMA observations of a strong gamma-ray flare
The launching mechanism of the jets of active galactic nuclei is
observationally poorly constrained, due to the large distances to these objects
and the very small scales (sub-parsec) involved. In order to better constrain
theoretical models, it is especially important to get information from the
region close to the physical base of the jet, where the plasma acceleration
takes place. In this paper, we report multi-epoch and multi-frequency continuum
observations of the z=2.5 blazar PKS1830-211 with ALMA, serendipitously
coincident with a strong -ray flare reported by Fermi-LAT. The blazar
is lensed by a foreground z=0.89 galaxy, with two bright images of the compact
core separated by 1". Our ALMA observations individually resolve these two
images (although not any of their substructures), and we study the change of
their relative flux ratio with time (four epochs spread over nearly three times
the time delay between the two lensed images) and frequency (between 350 and
1050 GHz, rest-frame of the blazar), during the -ray flare. In
particular, we detect a remarkable frequency-dependent behaviour of the flux
ratio, which implies the presence of a chromatic structure in the blazar (i.e.,
a core-shift effect). We rule out the possiblity of micro- and milli-lensing
effects and propose instead a simple model of plasmon ejection in the blazar's
jet to explain the time and frequency variability of the flux ratio. We suggest
that PKS1830-211 is likely one of the best sources to probe the activity at the
base of a blazar's jet at submillimeter wavelengths, thanks to the peculiar
geometry of the system. The implications of the core-shift in absorption
studies of the foreground z=0.89 galaxy (e.g., constraints on the cosmological
variations of fundamental constants) are discussed.Comment: Accepted for publication in A&
A Search for OH Megamasers at z > 0.1. I. Preliminary Results
We present the preliminary results of a survey for OH megamasers underway at
the Arecibo Observatory. The goals of the survey are to calibrate the
luminosity function of OH megamasers to the low-redshift galaxy merger rate
(0.1 < z < 0.2), and to use the enhanced sample of OH megamasers provided by
the survey to study OH megamaser environments, engines, lifetimes, and
structure. The survey should double the known OH megamaser sample to roughly
100 objects. Survey results will be presented in installments to facilitate
community access to the data. Here we report the discovery of 11 OH megamasers
and one OH absorber, and include upper limits on the isotropic 1667 MHz OH line
luminosity of 53 other luminous infrared galaxies at z > 0.1. The new
megamasers show a wide range of spectral properties, but are consistent with
the extant set of 55 previously reported objects, only 8 of which have z > 0.1.Comment: 18 pages, 3 figures, accepted for publication in the Astronomical
Journa
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