2,498 research outputs found
Star-Crossed Lovers DI Tau A and B: Orbit Characterization and Physical Properties Determination
The stellar companion to the weak-line T Tauri star DI Tau A was first
discovered by the lunar occultation technique in 1989 and was subsequently
confirmed by a speckle imaging observation in 1991. It has not been detected
since, despite being targeted by five different studies that used a variety of
methods and spanned more than 20 years. Here, we report the serendipitous
rediscovery of DI Tau B during our Young Exoplanets Spectroscopic Survey
(YESS). Using radial velocity data from YESS spanning 17 years, new adaptive
optics observations from Keck II, and a variety of other data from the
literature, we derive a preliminary orbital solution for the system that
effectively explains the detection and (almost all of the) non-detection
history of DI Tau B. We estimate the dynamical masses of both components,
finding that the large mass difference (q 0.17) and long orbital period
(35 years) make DI Tau system a noteworthy and valuable addition to
studies of stellar evolution and pre-main-sequence models. With a long orbital
period and a small flux ratio (f2/f1) between DI Tau A and B, additional
measurements are needed for a better comparison between these observational
results and pre-main-sequence models. Finally, we report an average surface
magnetic field strength () for DI Tau A, of 0.55 kG, which is
unusually low in the context of young active stars.Comment: 21 pages, 10 figures. Accepted to Ap
Empowerment or Engagement? Digital Health Technologies for Mental Healthcare
We argue that while digital health technologies (e.g. artificial intelligence, smartphones, and virtual reality) present significant opportunities for improving the delivery of healthcare, key concepts that are used to evaluate and understand their impact can obscure significant ethical issues related to patient engagement and experience. Specifically, we focus on the concept of empowerment and ask whether it is adequate for addressing some significant ethical concerns that relate to digital health technologies for mental healthcare. We frame these concerns using five key ethical principles for AI ethics (i.e. autonomy, beneficence, non-maleficence, justice, and explicability), which have their roots in the bioethical literature, in order to critically evaluate the role that digital health technologies will have in the future of digital healthcare
The XMM Cluster Survey: evolution of the velocity dispersion–temperature relation over half a Hubble time
We measure the evolution of the velocity dispersion–temperature (σv–TX) relation up to z = 1 using a sample of 38 galaxy clusters drawn from the XMM Cluster Survey. This work improves upon previous studies by the use of a homogeneous cluster sample and in terms of the number of high-redshift clusters included. We present here new redshift and velocity dispersion measurements for 12 z > 0.5 clusters observed with the Gemini Multi Object
Spectographs instruments on the Gemini telescopes. Using an orthogonal regression method,we find that the slope of the relation is steeper than that expected if clusters were self-similar, and that the evolution of the normalization is slightly negative, but not significantly different from zero (σv ∝T0.86±0.14E(z)−0.37±0.33). We verify our results by applying our methods to cosmological hydrodynamical simulations. The lack of evolution seen in our data is consistent with simulations that include both feedback and radiative cooling
Indication for the disappearance of reactor electron antineutrinos in the Double Chooz experiment
The Double Chooz Experiment presents an indication of reactor electron
antineutrino disappearance consistent with neutrino oscillations. A ratio of
0.944 0.016 (stat) 0.040 (syst) observed to predicted events was
obtained in 101 days of running at the Chooz Nuclear Power Plant in France,
with two 4.25 GW reactors. The results were obtained from a single 10
m fiducial volume detector located 1050 m from the two reactor cores. The
reactor antineutrino flux prediction used the Bugey4 measurement as an anchor
point. The deficit can be interpreted as an indication of a non-zero value of
the still unmeasured neutrino mixing parameter \sang. Analyzing both the rate
of the prompt positrons and their energy spectrum we find \sang = 0.086
0.041 (stat) 0.030 (syst), or, at 90% CL, 0.015 \sang 0.16.Comment: 7 pages, 4 figures, (new version after PRL referee's comments
Compressed representation of a partially defined integer function over multiple arguments
In OLAP (OnLine Analitical Processing) data are analysed in an n-dimensional cube. The cube may be represented as a partially defined function over n arguments. Considering that often the function is not defined everywhere, we ask: is there a known way of representing the function or the points in which it is defined, in a more compact manner than the trivial one
An Atlas of FUSE Sight Lines Toward the Magellanic Clouds
We present an atlas of 57 Large Magellanic Cloud (LMC) and 37 Small
Magellanic Cloud (SMC) observations obtained with the Far Ultraviolet
Spectroscopic Explorer (FUSE) satellite. The atlas highlights twelve
interstellar absorption line transitions at a resolution of ~15 km/s. These
transitions cover a broad range of temperatures, ionization states, and
abundances. The species included are OVI, which probes hot (T~3x10^5 K) ionized
gas; CIII and FeIII, which probe warm (T~10^4 K) ionized gas; SiII, PII, CII,
FeII, and OI, warm neutral gas; and six different molecular hydrogen
transitions, which trace cold (T<=500 K) gas. We include Schmidt Halpha CCD
images of the region surrounding each sight line showing the morphology of warm
ionized gas in the vicinity, along with continuum images near each FUSE
aperture position. Finally, we present several initial scientific results
derived from this dataset on the interstellar medium of the Magellanic Clouds
and Galactic halo.Comment: 29 pages, 6 figures. Complete Atlas of 94 additional images (~800kB
each) is available at http://fuse.pha.jhu.edu/~danforth/atlas Accepted to the
ApJS March 200
Do citations and readership identify seminal publications?
This work presents a new approach for analysing the ability of existing research metrics to identify research which has strongly influenced future developments. More specifically, we focus on the ability of citation counts and Mendeley reader counts to distinguish between publications regarded as seminal and publications regarded as literature reviews by field experts. The main motivation behind our research is to gain a better understanding of whether and how well the existing research metrics relate to research quality. For this experiment we have created a new dataset which we call TrueImpactDataset and which contains two types of publications, seminal papers and literature reviews. Using the dataset, we conduct a set of experiments to study how citation and reader counts perform in distinguishing these publication types, following the intuition that causing a change in a field signifies research quality. Our research shows that citation counts work better than a random baseline (by a margin of 10%) in distinguishing important seminal research papers from literature reviews while Mendeley reader counts do not work better than the baseline
High-density genetic mapping identifies new susceptibility loci for rheumatoid arthritis.
Using the Immunochip custom SNP array, which was designed for dense genotyping of 186 loci identified through genome-wide association studies (GWAS), we analyzed 11,475 individuals with rheumatoid arthritis (cases) of European ancestry and 15,870 controls for 129,464 markers. We combined these data in a meta-analysis with GWAS data from additional independent cases (n = 2,363) and controls (n = 17,872). We identified 14 new susceptibility loci, 9 of which were associated with rheumatoid arthritis overall and five of which were specifically associated with disease that was positive for anticitrullinated peptide antibodies, bringing the number of confirmed rheumatoid arthritis risk loci in individuals of European ancestry to 46. We refined the peak of association to a single gene for 19 loci, identified secondary independent effects at 6 loci and identified association to low-frequency variants at 4 loci. Bioinformatic analyses generated strong hypotheses for the causal SNP at seven loci. This study illustrates the advantages of dense SNP mapping analysis to inform subsequent functional investigations
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