71 research outputs found
Active paper for active learning
Recent research into distance learning and the virtual campus has focused on the use of electronic documents and computer‐based demonstrations to replace or reinforce traditional learning material. We show how a computer‐augmented desk, the DigitalDesk, can provide the benefits of both paper and electronic documents using a natural interface based on real paper documents. Many electronic documents, particularly those created using the guidelines produced by the Text Encoding Initiative (TEI), include detailed semantic and linguistic information that can be used to good effect in learning material. We discuss potential uses of TEI texts, and describe one simple application that allows a student's book to become an active part of a grammar lesson when placed on the DigitalDesk. The book is integrated into an interactive point‐and‐click interface, and feedback is related to the currently visible pages of the boo
SEGUE-2 Limits on Metal-Rich Old-Population Hypervelocity Stars In the Galactic Halo
We present new limits on the ejection of metal-rich old-population
hypervelocity stars from the Galactic center (GC) as probed by the SEGUE-2
survey. Our limits are a factor of 3-10 more stringent than previously
reported, depending on stellar type. Compared to the known population of B-star
ejectees, there can be no more than 30 times more metal-rich old-population F/G
stars ejected from the GC. Because B stars comprise a tiny fraction of a normal
stellar population, this places significant limits on a combination of the GC
mass function and the ejection mechanism for hypervelocity stars. In the
presence of a normal GC mass function, our results require an ejection
mechanism that is about 5.5 times more efficient at ejecting B-stars compared
to low-mass F/G stars.Comment: 18 pages including 5 figures; Submitted to Ap
Highly selective staining and quantification of intracellular lipid droplets with a compact push–pull fluorophore based on benzothiadiazole
A robust lipophilic dye, based on the structures of the benzothiadiazole heterocycle, was shown to be a potent fluorescent stain for the selective imaging of lipid droplets (LDs) within both live and fixed human cells. Its small molecular framework, large Stokes shift, and vastly improved photostability over that of the current status quo, Nile Red, highlight its tremendous potential as a versatile chemical tool for facilitating LD imaging and research
Fashionably Late? Building up the Milky Way's Inner Halo
Using a sample of 248 metal-poor stars (RR Lyraes, red giants and RHB stars)
which is remarkable for the accuracy of its 6-D kinematical data, we find a new
component for the local halo which has an axial ratio c/a ~ 0.2, a similar
flattening to the thick disk. It has a small prograde rotation but is supported
by velocity anisotropy, and contains more intermediate-metallicity stars (with
-1.5 < [Fe/H] < -1.0) than the rest of our sample. We suggest that this
component was formed quite late, during or after the formation of the disk. It
formed either from the gas that was accreted by the last major mergers
experienced by the Galaxy, or by dynamical friction of massive infalling
satellite(s) with the halo and possibly the stellar disk or thick disk. The
remainder of the stars in our sample exhibit a clumpy distribution in energy
and angular momentum, suggesting that the early, chaotic conditions under which
the inner halo formed were not violent enough to erase the record of their
origins. The clumpy structure suggests that a relatively small number of
progenitors were responsible for building up the inner halo, in line with
theoretical expectations. We find a difference in mean binding energy between
the RR Lyrae variables and the red giants in our sample, suggesting that more
of the RR Lyraes in the sample belong to the outer halo, and that the outer
halo may be somewhat younger, as first suggested by Searle and Zinn (1978). We
also find that the RR Lyrae mean rotation is more negative than the red giants,
which is consistent with the recent result of Carollo et al.(2007) that the
outer halo has a retrograde rotation and with the difference in kinematics seen
between RR Lyraes and BHB stars by Kinman et al.(2007).Comment: 16 pages, 10 figures, this version accepted by Ap
The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with
new instrumentation and new surveys focused on Galactic structure and chemical
evolution, measurements of the baryon oscillation feature in the clustering of
galaxies and the quasar Ly alpha forest, and a radial velocity search for
planets around ~8000 stars. This paper describes the first data release of
SDSS-III (and the eighth counting from the beginning of the SDSS). The release
includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap,
bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a
third of the Celestial Sphere. All the imaging data have been reprocessed with
an improved sky-subtraction algorithm and a final, self-consistent photometric
recalibration and flat-field determination. This release also includes all data
from the second phase of the Sloan Extension for Galactic Understanding and
Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars
at both high and low Galactic latitudes. All the more than half a million
stellar spectra obtained with the SDSS spectrograph have been reprocessed
through an improved stellar parameters pipeline, which has better determination
of metallicity for high metallicity stars.Comment: Astrophysical Journal Supplements, in press (minor updates from
submitted version
Leukocyte Telomere Length in Major Depression: Correlations with Chronicity, Inflammation and Oxidative Stress - Preliminary Findings
Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of “accelerated aging” in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD), whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation.Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio) and inflammation (IL-6). Analyses were controlled for age and sex.The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05). Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration) was 281 base pairs shorter than that in controls (p<0.05), corresponding to approximately seven years of “accelerated cell aging.” Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01) and in the controls (p<0.05) and with inflammation in the depressed subjects (p<0.05).These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression and is not an intrinsic feature. Rather, telomere shortening may progress in proportion to lifetime depression exposure
Erratum: “The eighth data release of the Sloan Digital Sky Survey: first data from SDSS-III” (2011, ApJS, 193, 29)
Section 3.5 of Aihara et al. (2011) described various sources of systematic error in the astrometry of the imaging data of the Sloan Digital Sky Survey (SDSS). In addition to these sources of error, there is an additional and more serious error, which introduces a large systematic shift in the astrometry over a large area around the north celestial pole. The region has irregular boundaries but in places extends as far south as declination δ ≈ 41◦. The sense of the shift is that the positions of all sources in the affected area are offset by roughly 250 mas in a northwest direction. We have updated the SDSS online documentation to reflect these errors, and to provide detailed quality information for each SDSS field
SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II),
SDSS-III is a program of four spectroscopic surveys on three scientific themes:
dark energy and cosmological parameters, the history and structure of the Milky
Way, and the population of giant planets around other stars. In keeping with
SDSS tradition, SDSS-III will provide regular public releases of all its data,
beginning with SDSS DR8 (which occurred in Jan 2011). This paper presents an
overview of the four SDSS-III surveys. BOSS will measure redshifts of 1.5
million massive galaxies and Lya forest spectra of 150,000 quasars, using the
BAO feature of large scale structure to obtain percent-level determinations of
the distance scale and Hubble expansion rate at z<0.7 and at z~2.5. SEGUE-2,
which is now completed, measured medium-resolution (R=1800) optical spectra of
118,000 stars in a variety of target categories, probing chemical evolution,
stellar kinematics and substructure, and the mass profile of the dark matter
halo from the solar neighborhood to distances of 100 kpc. APOGEE will obtain
high-resolution (R~30,000), high signal-to-noise (S/N>100 per resolution
element), H-band (1.51-1.70 micron) spectra of 10^5 evolved, late-type stars,
measuring separate abundances for ~15 elements per star and creating the first
high-precision spectroscopic survey of all Galactic stellar populations (bulge,
bar, disks, halo) with a uniform set of stellar tracers and spectral
diagnostics. MARVELS will monitor radial velocities of more than 8000 FGK stars
with the sensitivity and cadence (10-40 m/s, ~24 visits per star) needed to
detect giant planets with periods up to two years, providing an unprecedented
data set for understanding the formation and dynamical evolution of giant
planet systems. (Abridged)Comment: Revised to version published in The Astronomical Journa
International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways.
Primary biliary cirrhosis (PBC) is a classical autoimmune liver disease for which effective immunomodulatory therapy is lacking. Here we perform meta-analyses of discovery data sets from genome-wide association studies of European subjects (n=2,764 cases and 10,475 controls) followed by validation genotyping in an independent cohort (n=3,716 cases and 4,261 controls). We discover and validate six previously unknown risk loci for PBC (Pcombined<5 × 10(-8)) and used pathway analysis to identify JAK-STAT/IL12/IL27 signalling and cytokine-cytokine pathways, for which relevant therapies exist
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